Conventionally known is an electronic lock which is locked when powered (Patent reference 1, for example). An electronic lock, disclosed in Patent reference 1, is locked when electric power is supplied and unlocked when electric power supply is interrupted. Therefore, when power outage occurs and electric current supply to the electronic lock is interrupted, the lock is automatically unlocked. Conventionally also known is an electronic lock which is unlocked when powered. This type of electronic lock is unlocked when electric power is supplied and locked when electric power supply is interrupted. Therefore, this type of electronic lock is automatically locked when power outage occurs and electric current supply to the electronic lock is interrupted.